Interactions With Other Organisms

Interactions with Humans

Bromus hordeaceus is one of plenty of species that are very problematic in many different continents. This Brome invades fields that are good for farming and interrupts the growth and nutrient acquisition of the surrounding crops (Andersson et al. 2002). This is harmful to humans in that it makes it harder for farmers and gardeners to grow crops because its seeds can remain ungerminated for over a year in the soil and emerge after the soil has been sowed, in other words, Bromus hordeaceus's seeds can remain dormant for over a year (Andersson et al. 2002).

Symbiotic Mutualism

Organism that have a mutualistic and symbiotic relationship with Bromus hordeaceus's roots are endomycorrhizal fungi, specifically arbiscular mycorrhizal fungi, which can actually help the grass’s roots grow and help increase the reproductive rates of the grass (Antolin 2008). We do not know what specific species of arbiscular mycorrhizal fungi have this relationship with Bull Grass, but the fungi that do this are from the Glomeromycota phylum. If you take Organismal Biology (at UW-La Crosse, BIO 203), you would learn about mycorrhizal and endomycorrizal fungi having these kinds of relationships with plants; mycorrhizal and endomycorrhizal fungi lower the Used with permission from Keir Morse resources used by the plants in making roots because the fungi will help increase the amount of resources that the plants' roots absorb by increasing their roots' surface area in exchange for resources that the fungi would need. They also protect plants' roots. Having a symbiotic and mutualistic relationship means that both organisms are living together where both benefit from each other, and this relationship definitely describes that between arbiscular fungi and Bromus hordeaceus.


In many areas of California and southwestern Oregon (more information in the Habitat page), Bromus hordeaceus is one of two dominant annual plants; the other being the Broad-leaved filaree (Erodium botrys) which has codominance with B. hordeaceus (Howard 1998). "Red brome (B. rubens) and Cutleaf filaree (E. cicutarium)" generally replace "Soft chess and Broad-leaved filaree as dominants in portions of the Central Valley..." (Howard 1998). Another competitor is Bromus tectorum or Cheatgrass (also mentioned in the Habitat page)


Soft cheat (one of the common names for Bromus hordeaceus) does not have any predatory interactions itself, but it is invasive and harmful to some native organisms in the areas where it has been introduced as a non-native organism (Ainouche et al. 1999).

Being an autotrophic organism, or a producer, Soft chess (another one of the common names for Bromus hordeaceus) acquires its food from the soil and from the sun through photosynthesis and nutrient uptake with the aid of water cohesion. Because it is a producer and on the bottom of the food web, many organisms (mainly herbivores) eat Bromus hordeaceus such as cattle, deer (like the White-Tailed Deer), domestic goats, horses, rabbits, domestic sheep, other small mammals, and some birds (Howard 1998). Picture taken by Dr. Thomsen. Used with Permission.

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